Position location systems for mobile devices in satellite positioning challenged/denied areas may use positioning based on signals from local wireless transmitters, such as cell towers or base stations for cellular wireless networks, access points for wireless local area networks (WLANs) or wireless personal area networks (WPANs), etc. Positioning using wireless transmitters conventionally requires an assistance server that can provide an almanac that contains the locations of the wireless transmitters.
Conventionally, almanac databases are built using crowdsourcing, wardriving and/or a combination of both. Crowdsourcing and wardriving require that multiple mobile devices collect data related to the location of the wireless transmitters and submit the collected data to a centrally located server. The server combines the collected data from multiple users to generate the almanac database that includes the locations of the wireless transmitters. In order to use wireless transmitters for positioning, a mobile device accesses the almanac database through the server, or different servers, and uses the locations for visible wireless transmitters to determine the position of the mobile device.
A source of error when generating the almanac database is the inclusion of wireless transmitters that do not have a fixed or static location. For example, crowdsourcing or wardriving may collect and forward to the server location related data for mobile wireless transmitters, such as mobile hotspot access points, mobile Bluetooth tags or mobile cell tower identifies. Inclusion of mobile wireless transmitters in the almanac database may result in location errors if these mobile wireless transmitters are used to compute a position fix after the mobile wireless transmitters have moved.